Space to rest your palms. Length so that it's comfortable to sit in your lap. Space inside the case for the stick and buttons to fit comfortably. Ergonomics. I hate the alpha. I wouldn't want my stick and buttons to be so close, that's hella uncomfortable for me. I love larger sticks. It's one of the reasons I don't like the HRAP case and can't wait for the fightingedge. can comfortably rest my hands on the case without it hanging off, super solid feel on the plexi, and a striking design.
The MKX stick is based on an american stick and those buttons and sticks take up more space in the case.
Ok i can see your points but i still think that some space could be cut while keeping enough space for all the pros you like so much, maybe i just don't know what i'm talking about since i don't have one(but i used to go to arcades! XD )
EDIT:
I didn't think about that! :OMany prefer a larger heavier arcade stick. Especially if you're going to be playing with it on your lap. Also, extra space on the play area of the controller helps accommodate additional grip/play styles.